Commonly, the flow rate of combustion air supplied to a gas turbine is controlled through the opening of inlet guide vanes (IGVs) etc. The opening of the IGVs is smaller during no load operation or partial load operation of the gas turbine than during rated load operation. Especially when the atmospheric temperature falls in winter, an icing phenomenon of moisture in the air forming ice may occur at the inlet part of the compressor. When the icing phenomenon occurs, not only is the reliability of the gas turbine adversely affected due to the resulting decrease in output and efficiency of the gas turbine, but also the blades and vanes in a front stage of the compressor may be damaged as the accumulated ice falls away.
To avoid this phenomenon, there have been proposed various gas turbines and operation methods thereof for anti-icing operation in which the temperature of intake air entering the compressor is raised. Patent Literature 1 shows one example of a bleed air circulation method for anti-icing purposes, in which part of casing air is extracted from a casing where air having been compressed in the compressor and reached high temperature is stored, and that part of casing air is circulated to an air intake facility on the inlet side of the compressor to raise the temperature of air entering the compressor and thereby prevent the icing phenomenon.
Regarding a gas turbine that performs normal operation without anti-icing operation, Patent Literature 2 shows one example of a system and a method in which combustion in a gas turbine is controlled on the basis of the turbine inlet temperature.